<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            padding: 0;
            margin: 0;
            list-style: none;
        }
        ul{
            display: grid;
            width: 300px;
            height: 300px;
            grid-template-columns: repeat(3,1fr);
            grid-template-rows: repeat(3,1fr);
            gap: 5px 5px;
        }
        li{
            width: 100px;
            height: 100px;
            border: 1px solid #000;
        }
        li:nth-child(4){
            grid-column: 1/3;
            width: 100%;
        }
        li:nth-child(6){
            grid-row: 2/4;
            height: 100%;
            grid-column: 3;
        }
    </style>
</head>
<body>
    <ul>
        <li>第1</li>
        <li>第2</li>
        <li>第3</li>
        <li>第4</li>
        <li>第5</li>
        <li>第6</li>
        <li>第7</li>
    </ul>
</body>
</html>